docs: def removeReference(self, fromnode, tonode):
          """
          Remove all edges from fromnode to tonode
          """
          if fromnode is None:
              fromnode = self
          fromident = self.getIdent(fromnode)
          toident = self.getIdent(tonode)
          if fromident is not None and toident is not None:
              while True:
                  edge = self.graph.edge_by_node(fromident, toident)
                  if edge is None:
                      break
                  self.graph.hide_edge(edge)